Thanks David! It's great to see that this will be disabled in modes where we *know* the machine is shared.
Fergal - could you address concerns about web developer advice? What should we tell web developers to do on their logout pages? On Fri, Nov 10, 2023 at 8:37 AM David Dworken <ddwor...@google.com> wrote: > Chiming in to say that we discussed the security concerns around this > proposal quite extensively internally and overall we believe that with the > short timeout, the security risks are acceptable. The residual security > risk is for servers that implement purely server-side logouts and is only > exploitable for a very short period of time (3 minutes). In addition, other > mitigations like this one > <https://bugs.chromium.org/p/chromium/issues/detail?id=1468438> further > reduce the risk such that we believe it is unlikely that this will lead to > new security issues. > > On Friday, October 13, 2023 at 7:14:46 AM UTC-7 vmp...@chromium.org wrote: > > On Fri, Oct 13, 2023 at 12:00 AM 'Fergal Daly' via blink-dev < > blin...@chromium.org> wrote: > > On Thu, 12 Oct 2023 at 23:05, Yoav Weiss <yoav...@chromium.org> wrote: > > > > On Thu, Oct 12, 2023 at 3:56 PM Vladimir Levin <vmp...@chromium.org> > wrote: > > Are there any spec changes planned for this feature? I'm not sure if the > README linked under Specification is meant to make it into WHATWG, maybe to > close out https://github.com/whatwg/html/issues/7189 > > The only spec I could find about CCNS is > https://www.rfc-editor.org/rfc/rfc9111#section-5.2.1.5, so I'm not sure > how to reconcile possibly contradicting language in the specs > > > Great questions! Fergal - can you answer that? > > > RFC9111 is about HTTP caches. BFCache is not a HTTP cache, so RFC 9111 > does not apply. Of course the reality of implementations and expectations > vs spec is a problem. Some more discussion here > <https://github.com/fergald/explainer-bfcache-ccns/blob/main/README.md#current-interactions-between-bfcache-and-ccns> > > > I'm not sure I agree with this, or the reasoning in the link. First of > all, this intent thread is about ignoring CCNS in _some cases_. In other > cases, CCNS is respected, so it seems like BFCache is de facto subject to > RFC 9111. > > This is, I guess, a bit philosophical but the spec says: > the cache MUST NOT intentionally store the information in non-volatile > storage and MUST make a best-effort attempt to remove the information from > volatile storage as promptly as possible after forwarding it. > > Note that the spec here does not make any exceptions for things like > cookie state not changing or anything else. The document when frozen is > indeed a volatile storage of the server response, processed and stored in > some particular format (ie the DOM tree). I admit it's a bit weird to think > about it this way, since the live document is technically also this cache. > Whereas I agree that BFCache is not strictly an HTTP Cache, I don't quite > follow why CCNS should not apply to the BFCache in some cases. > > To me, BFCache seems like "a better http cache" which already has rendered > results, not a completely separate cache that is not subject to CCNS. > > But I'm late to the game, and I see that the topic of "BFCache is not HTTP > Cache" has already been discussed a lot. I'm not convinced by existing > arguments, but I also don't think I'll be able to convince anyone of my > position. > > My problem with the consensus in > https://github.com/whatwg/html/issues/5744 is the following. People seem > to agree that we don't want a *new* api that specifically prevents pages > from entering BFCache. I don't believe it's appropriate to draw a > conclusion that there is consensus that BFCache should not be subject to > any *existing* APIs that prevent pages from entering it. This might be true > independently, but I don't think one follows from the other. To quote this > comment > <https://github.com/whatwg/html/issues/5744#issuecomment-811958634>: > "... And what is the problem with the bank case? I'd expect bank may want > to ensure its page doesn't enter bfcache, or any other cache, by using > no-store (and other) header(s) or something ..." > > That comment sounds to me like "the status quo is good enough, because > there are already ways of preventing any cache, including bfcache." If we > were to claim consensus on doing this work, I'd personally want to see a > more explicit "let's make it so pages still enter BFCache despite CCNS in > these cases." The comment from cdumez you quoted is good, but maybe > following-up there is worthwhile. > > > I concede though that I'm by no means an expert here, so I don't want to > block moving this forward any longer. I just want to say that it's > typically easy to be fast if you show stale data, and shifting the blame to > the site for using CCNS instead of refreshing needed content in script > doesn't seem appropriate. I personally would not want to be the judge of > whether CCNS use is appropriate or not since I don't know what > "appropriate" is in this case. > > > > > BFCache and cases where it can/can't be used are specced in the HTML > standard. We have had very little engagement from other vendors on this > particular idea but Safari tried to cache all CCNS pages in the past. I am > hoping that if we demonstrate a way to cache some of them safely, they > would be on board. Also any browser is free to be *more* conservative than > the spec while still staying in-spec as BFCaching at all is always optional. > > Here <https://github.com/whatwg/html/issues/5744#issuecomment-661997090> > is cdumez of Safari > > Safari / WebKit shipped with all pages going into the bfcache no matter > what (including cache-control: no-store). The only push back we received > was the fact that after you log out of a site, you could still go back and > see a page you should no longer be able to see. We agreed that this > feedback was valid and our short-term fix was to bypass the bfcache when > the page uses cache-control: no-store. Sadly, many sites use this and > their intention is likely not to prevent the bfcache. This is not something > we like for the long term. > > F > > > > > Also, Vlad previously asked about the recommended pattern for folks to > handle credential revocation with BFCache and his concerns with the snippet > suggested upthread. It'd be great to address that. > > > Thanks! > vmpstr > > On Thu, Oct 12, 2023 at 2:32 AM Yoav Weiss <yoav...@chromium.org> wrote: > > I just discussed this with Fergal offline: > > - The risky scenario is one where revocation of sensitive info > (logout, access revoked) happens on the server-side only without a > client-side update. > - In such a scenario on a shared computer, someone could back-button > their way into someone else's sensitive info. > - It might be interesting to talk to security folks (and maybe Project > Zero folks) to see if this is not happening already with content that's not > CCNS decorated. > - It would be good to run a survey of potentially-sensitive services > and try to get a signal from them on how many of them are properly doing > revocation on the client side. > - I'd love ideas on how we can scale such a survey beyond manual > inspection of a few known services. > - It could be interesting to try and ship a version of this with a > shorter timeout, to minimize the risk of users leaving the machine > unattended. > - If we go that route, it'd be good to think through how we'd be > able to increase that timeout over time, after gaining more confidence > that > the risky scenario isn't happening in the wild. > > > > On Thu, Oct 5, 2023 at 2:36 AM Jason Robbins <jrob...@google.com> wrote: > > At this morning's API Owners meeting, they asked me to add all review gate > types to all of the "web developer facing code change" features that are > currently under review, including this one. So, I have added Privacy, > Security, Enterprise, Debuggability, and Testing gates to your feature > entry. > > Please click the gate chips in the "Prepare to ship" stage on your feature > detail page. For each one, answer survey questions and request that of the > cross-functional review. You can request them all in parallel. In cases > where you already have the go/launch <https://goto.google.com/launch> bit > approved, you can note that in a comment on that gate for a potentially > faster review. > > Thanks, > jason! > On Monday, October 2, 2023 at 9:09:18 AM UTC-7 Jason Robbins wrote: > > On Friday, September 29, 2023 at 1:01:54 PM UTC-7 Chris Harrelson wrote: > > Please also make sure to complete all of the other shipping gate reviews > <https://groups.google.com/a/chromium.org/g/blink-dev/c/bqvB1oap0Yc/m/YlO8DEHgAQAJ> > . > > > I think a bug in ChromeStatus may have caused some confusion on this > feature entry. The feature entry has type "Web developer facing code > change", so its bilnk-dev thread should have had subject line prefix > "Web-facing change PSA" rather than "Intent to ship". And, according to > the launching-features doc > <https://www.chromium.org/blink/launching-features/#psa-prepare-to-ship>, > it does not require any approvals, which is why there are no other gates > offered in the ChromeStatus UI. A fix for that subject-line prefix bug > should go live today. > > Of course, the point of a PSA is to allow concerns to be raised and I see > that this is a very active thread. So, all that should be worked through. > Its a mater of the the API Owners prerogative to request any other reviews > that they think are appropriate, but it is not automatically required by > the process for this feature type. Also, I see that the launch entry > <https://launch.corp.google.com/launch/4251651> had some approvals. > > Thanks, > jason! > > -- > You received this message because you are subscribed to the Google Groups > "blink-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to blink-dev+...@chromium.org. > To view this discussion on the web visit > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfUszpq%3DS%3DOZ4k_GnopJMRcTnL_trq5iF8J-kAzeYEiqKA%40mail.gmail.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfUszpq%3DS%3DOZ4k_GnopJMRcTnL_trq5iF8J-kAzeYEiqKA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > -- > You received this message because you are subscribed to the Google Groups > "blink-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to blink-dev+...@chromium.org. > > To view this discussion on the web visit > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAAozHLkA5eFwcvRsTAZhy728KFaBjd5W5EZpP2%3DMmC42ngMUuQ%40mail.gmail.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAAozHLkA5eFwcvRsTAZhy728KFaBjd5W5EZpP2%3DMmC42ngMUuQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to blink-dev+unsubscr...@chromium.org. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfWcv8yG0w-yeYMd6KMj%3DfRLR7uy1y%3D8sK_fsGkD1s%3Dq2g%40mail.gmail.com.
